What Does COVID-19 Mean for Building Operations?
As businesses are re-opening or workers are returning to offices, the attention of many has turned to the operation of buildings to help reduce the risk of new outbreaks. We’ve had a number of conversations with clients asking for our recommendations for operating buildings during this pandemic. Because of Command Commissioning’s background in HVAC system operation, occupant comfort and high performance we’ve pulled together a few resources to help.
The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) released a Position Document on April 14th, 2020 to address infectious aerosols and what effect HVAC systems can have on infectious disease transmission in occupied indoor spaces. We’d recommend reading through the entire publication, but here are a few of our takeaways:
- HVAC ventilation-related strategies are just one of several effective methods to reduce the risk of transmission and include: dilution (providing outside air into the building), airflow patterns, pressurization, temperature, humidity distribution and control, filtration and ultraviolet light.
- Thermal stress of occupants can result in decreased infection resistance so disabling HVAC systems or operating outside the ranges provided in ASHRAE standards for outdoor airflow rates (ASHRAE 62.1) or temperature and humidity setpoints (ASHRAE 90.1) is not recommended.
- Larger particles are localized (within 3-7ft from the source) and land on surfaces. As a result, ventilation strategies do little to mitigate transmission in this form. However, smaller aerosols suspended in the air can travel much further. Ventilation strategies that create clean-to-dirty flow patterns, capture particles through filtration and exhaust infectious aerosols work well to reduce the risk of transmission.
- UV-C is highly effective for inactivating microorganisms. The effectiveness of solutions that expose central AHU supply airflow to UV-C depend on the exposure time and intensity but the ability to minimize infectious aerosols such as SARS-CoV-2 is not yet known.
Based on our review of this document and experience with building HVAC and control systems, our general recommendations are:
- Consider increasing the efficiency rating of mechanical filters in central AHUs
- Consider installing UV-C on the supply side of central AHUs to inactivate microorganisms
- Adhere to standard thermal comfort temperature and humidity ranges
- Develop a temporary operating plan in response to an outbreak within the building occupants that includes increasing outside airflow rates and operating systems continuously
In addition to HVAC control or configuration recommendations, the following resources provide solutions for building operations to reduce the risk of infectious disease transmission.
CDC: Plan for cleaning and disinfecting workplaces
EPA: Information on disinfectants for use against SARS-CoV-2